Shielded dielectric heating apparatus



Sept. 23, 1969 R- M. SEROTA SHIELDED DIELECTRIC HEATING APPARATUS 2 Sheets-Sheet 1 Filed March 15, 1967 INVENTOR. RUDOLPH M. SERO TA 0 flwmzllyg'l um ATTORNEYS 2 Sheets-Sheet 2 INVENTOR RUDOLPH M. .SEROTA ym fiwuzmm ATTORNEYS R- M. SEROTA SHIELDED DIELECTRIC HEATING APPARATUS Sept. 23, 1969 Filed March 15, 1967 United States Patent 3,469,054 SHIELDED DIELECTRIC HEATING APPARATUS Rudolph M. Serota, East Cleveland, Ohio, assignor to Bangor Punta Operations, Inc., Bangor, Maine, a corporation of New York Filed Mar. 15, 1967, Ser. No. 623,376 Int. Cl. Hb 9/06 US. Cl. 219--10.61 7 Claims ABSTRACT OF THE DISCLOSURE A dielectric heating apparatus provided with shield means above and below the system electrodes for collecting high-frequency wave energy and conductmg the same to ground. The upper shield means is constructed and arranged for pivotal movement on the apparatus to permit threading of the dielectric web material through the apparatus. The lower shield forms an integral part of the tank circuit and functions to advantageously limit principal current flow to the interior shield members.

The present invention relates generally to dielectric heating apparatus and, more particularly, to the provision of novel shielding means in combination with such apparatus for effectively confining generally within such apparatus the relatively high-frequency wave energy produced thereby.

The dielectric heating apparatus of the type here concerned finds particularly advantageous use in the drying of traveling dielectric web material such as paper and the like. For optimum results, the operating frequency of the apparatus is desirably in the radio range, with twelve megacycles being a typical operating frequency. As a result, stray wave energy unavoidably produced during operation of the apparatus at the noted high frequencies and any multiples thereof is a source of potential interference to receiving equipment in the adjacent vicinity, a problem well understood by those skilled in the art. Such receiving equipment may commonly include radio and television receivers, or industrial equipment operating in frequency ranges likely to be affected by this stray radio energy. Further, unconfined radio energy, if produced at suificiently high power levels, may pose a potential radiated hazard to operating personnel in close range of the apparatus.

With the above in mind, a primary object of the present invention is to provide a shielding assembly for dielectric apparatus of the general type referred to for collecting the stray high-frequency wave energy and conducting the same through the apparatus to ground.

Another object of the present invention is to provide such a shielding assembly, the construction of which does not interfere with the-dielectric web maten'al traversing the apparatus.

A further object of the invention is to provide a shielding assembly which additionally serves to protect the operator from radiation and prevent physical contact with the high potential electrodes. At the same time, the shielding assembly functions to protect the equipment by preventing the entrance of dirt, dust, etc., into the interior thereof.

Yet another object of the present invention is to provide a shielding assembly which constitutes an essentially constant capacitive load which, once accounted for in tuning the generating apparatus, will be maintained constant, thereby preventing proximately located objects from detuning the system or causing uneven distribution within the system.

A still further object of the present invention is to provide such a shielding assembly which includes a top cover hingedly carried by the apparatus for convenient movement away from its operative position relatively adjacent the electrodes to permit access to the area immediately above the electrodes to facilitate threading of the dielectric web material over said electrodes.

These and other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawings:

FIG. 1 is a top plan view of the apparatus of the present invention;

FIG. 2 is a front elevational view of the apparatus of the present invention, with a certain portion of the apparatus being broken away to expose the interior of the apparatus;

FIG. 3 is an end elevational view of the apparatus, with a certain portion thereof being broken away to expose the interior of the apparatus;

FIG. 4 is a perspective View of the shield cover of the apparatus, with the cover being fragmentarily broken away in certain sections better to illustrate the construction thereof, and

FIG. 5 is a fragmentary, enlarged view of the upper righthand corner of FIG. 3.

Referring now in more detail to the drawings, wherein like reference numerals are employed to indicate like parts, the dielectric apparatus of the present invention comprises a bottom frame assembly including longitudinally extending channel frame members 10 and 11 and transverse channel frame members 12 and 13, which are rigidly interconnected to provide a rugged base frame. Although not illustrated in the drawing, it will be understood that the base frame is in turn supported by suitable supporting equipment at the installation site, with the particular support thus provided forming no part of the present invention and being variable as desired to accommodate particular installation requirements.

Vertically extending corner posts commonly designated at 14 extend upwardly from the lower frame at each corner thereof, with such corner posts receiving and supporting longitudinally extending top frame members 15 and 16 and transversely extending frame members 17 at opposite ends of the frame, with only one of such transverse frame members being visible in the application drawings.

Additional vertical supporting members commonly designated at 18 extend between the top and bottom longitudinal frame members 10, 11 and 15, 16 in longitudinally spaced relation to provide further support for the upper frame members. Similarly, supplementary vertical supporting members commonly designated at 19, FIG. 3, extend between the transverse bottom frame members 12, 13 and the transverse top frame members 17 for further supporting the top frame members in such regions. The frame members as thus described provide a rugged, box-like frame assembly. The frame assembly just described is completely enclosed by metallic sheeting material 20 suitably attached to the frame members by means of bolts 21 or the like.

A series of longitudinally extending ground electrodes extend between and are supported by the top transverse frame members 17 in any suitable manner. As clearly seen in FIG. 3, the electrodes 22 are planar and parallel and are connected to ground through the frame assembly.

Alternately interposed between the spaced ground electrodes 22 are a series of electrically charged electrodes commonly designated at 23. The electrodes 23 are supported intermediate their length by vertically extending rod members commonly designated at 24 which are in turn supported by transversely extending channel members 25 and 26. It will be noted that in the form shown, the charged electrodes 23 are coplanar with the ground electrodes 22.

The channel supporting members 25 and 26 are supported at their opposite ends by posts commonly designated at 27 which are in turn supported by lower transverse channel members 28 and 29 mounted at opposite sides of the frame to posts 18 in any suitable manner, for example by welding or the like. The posts 27 are insulated from the frame so as not to ground the charged electrodes 23. Although in the form shown the charged rods 23 are thus fixedly mounted relative to the frame, the charged electrodes could be mounted for vertical adjustment as shown in applicants pending application Ser. No. 499,754, filed Oct. 21, 1965, and entitled Dielectric Apparatus for and Method of Treating Traveling Paper Webs and the Like.

A variable vacuum capacitor, also disclosed in my pending application referred to above, is generally indicated at 30 and is mounted by means of a bracket 31 to an electrode plate 32 the opposite ends of which are mounted to the channel members 25 and 26. A source of high voltage energy is delivered to the variable vacuum capacitor by means of a supply pipe 33, with the capacitance of the capacitor 30 being mechanically adjustable in a well-known manner. The pipe 33 passes outwardly from the frame through a trunnion assembly generally indicated at 35 which is adapted to permit rotation of the entire frame about an axis through the trunnion. It will be understood by those skilled in the art that it may be desirable in certain operating conditions to pass the Web over the electrodes in an orientation other than horizontal and the trunnion assembly is adapted to provide such adjustment.

The opposite end of the frame is supported by means of a pipe or shaft 36 which is mounted to the frame by flange 37 in turn connected to the vertical supporting channels 19, FIG. 3. The free end of the shaft 36 can be suitably supported for rotation, for example by pivot block 38 or the like, shown in dashed lines in FIG. 2. The shaft can be rotated by any suitable means, for example by a motor or the like mounted at such end of the apparatus. An intake manifold 39 is mounted on the frame generally outwardly from the ends of the electrodes 22 and 23.

The operation of the apparatus thus far described is as follows. The web of dielectric material, such as paper or the like, is passed transversely over the alternately disposed, parallel electrodes 22 and 23. Voltage is supplied to the charged electrodes 23 through the variable vacuum capacitor 30 thereby to establish a voltage gradient between each adjacent pair of charged and grounded electrodes. The voltage delivered to the charged electrodes can be effectively controlled by the variable vacuum capacitor 30 to provide optimum heating, and thus drying, of the web material. As noted above, the apparatus of the present invention is designed primarily for operation in the radio-frequency range, with 12 million cycles per second being typical. At such operating frequencies, stray radio energy is a potential interferent with equipment in the general area adjacent the installation.

' In accordance with the invention, shielding means are provided above and below the electrodes for receiving such stray radio energy and conducting the same to ground through the frame. A lower shield member generally indicated at 40 generally coextensive in dimension with the entire frame is mounted to the frame below the electrodes. The lower shield 48 includes a flat bottom section 41, upwardly inclined longitudinal end sections 4 42 and 43, and transverse, upwardly inclined side sections 44 and 45.

The ends 42 and 43 are formed with laterally extending flanges commonly designated at 46 which are disposed contiguous the bottom flange of channel member 17, FIG. 2, and connected thereto by bolts 47 or the like. In a similar manner, the sides 44 and 45 are provided with lateral flanges commonly designated at 48, shown enlarged in FIG. 5, disposed contiguous the bottom flanges of the channel members 15 and 16 and secured thereto by mounting bolts 49. Referring to FIG. 2, the power supply pipe 33 is supported intermediate the ends thereof by means of the inductance branch 52 of the generator tank circuit of the system. The inductance branch 52 has a lower flange 53 mounted on and, electrically connected to the bottom section 41 of the lower shield 40. It will thus be seen that the lower shield 40 forms an integral part of the tuned circuit, with the principal circulating current flow being directed through the lower shield rather than the exterior frame members.

The upper shield for the electrodes is in the form of a hinged shield cover generally indicated at 60, with hinge brackets 61 being carried by the cover adjacent one end thereof for pivotal mounting of the cover to upwardly extending arms 62 carried by the apparatus frame.

As perhaps best shown in the perspective FIG. 4 view, the cover 60 comprises an inner sheet metal member 64 which is the principal current carrying member of the upper shield, member 64 having longitudinal side edges 65 extending normal to the plane of the member, and downwardly and outwardly inclined front and rear flanges 66 at opposite ends of the member.

A channel frame assembly extends around the inner member 64 in spaced relation thereto. The channel frame assembly includes longitudinal channel members commonly designated at 68 and transverse channel members commonly designated at 69, with the adjoining edges of such channel members being suitably connected to form a rectangular channel frame.

As best seen in FIG. 4, the inclined end sections 66 of the inner member 64 are provided with forwardly directed horizontal flanges 70 which extend below the bottom flanges 71 of the end channel members 69, with such contigous flanges being secured in any suitable manner, for example by bolts or the like (not shown). The inner member 64 is thus carried by the outer channel frame in spaced relation thereto. The channel members 68 and 69 above discussed are preferably of aluminum, and the inner member 64 is preferably of sheet aluminum. A top cover 75 also preferably of sheet aluminum, and dimensionally coextensive with the exterior dimension of the channel frame assembly comprising the channel members 68 and 69, is secured to the later in any suitable manner, such as by welding or the like.

Referring to FIG. 5, the vertically downwardly depending side edges 65 of the inner member 64 are provided with longitudinally spaced tapped openings adapted to be aligned with slots or grooves 81 formed in the vertical leg 82 of an L-shaped angle member 83. Adjusting bolts 84 are adapted to extend through the aligned slots and tapped openings formed in these respective members to permit vertical adjustment of the angle member 83 to any vertically desired position.

In a similar manner, the longitudinal channel members 68 are provided with a series of spaced tapped openings in alignment with slots 91 formed in angle members 92 disposed contiguous the webs of the frame members 68. Adjusting bolts 93 are provided for vertically adjusting the angle members 92 relative to the channel frame members 68.

In a similar manner, angle member 96 is adjustably carried by the channel member 15, with the former having a series of slots 98 and the latter being provided with a series of spaced tapped openings 97. Clamping bolts 99 are provided to secure such adjustable attachment. The angle 96 can thus be vertically adjusted to the degree desired above the electrodes 22 and 23.

It will thus be seen that the angles 92 and 96 define at each end of the apparatus a rectangular opening 100 through which the web W passes in traveling to and from the apparatus. The respective angle members can be adjusted toward or away from each other to provide the minimum practical opening depth to be determined by the type of web material and condition encountered and the angle 96, as noted, can be vertically adjusted to, if desired, support the web W at varying distances from the charged and grounded electrodes 23 and 22, respectively. It will be understood that normally the web is tensioned and supported exteriorly of the applicator.

The free end of the cover 60 is provided with handle means 102 and 103 at opposite sides thereof. As perhaps best seen in FIG. 3, the handles are pivotally carried by brackets 104 mounted to side plates 105 carried by. the cover. The handles 102 and 103 mount generally U-shaped brackets 106 the arms of which receive therebetween pins 107 and 108, FIG. 4. A latch bracket 109 is mounted on either side of the frame with the outer end thereof being in the form of a shoulder under which the pin 107 can extend. In this manner, manipulation of the handles 102 and 103 effectively latches the cover 16 in place or releases the same for hinged movement about the hinged end thereof.

Referring to FIGS. 1 and 2, the apparatus frame at the longitudinal ends thereof carry upwardly directed support angles 110 and 111 the top flanges of which extend inwardly of the frame. The previously described channel frame members 69 of the cover 60 are vertically aligned with such inwardly turned flanges of the angles 110 and 111 and are adapted to be supported thereby thus to vertically space the cover 60 relative to the frame.

It will be seen that the cover 60 is connected to the frame in several regions whereby the cover is at all times connected to ground through the frame. As a result, stray radio energy emanating from the electrodes in the region of the cover is conducted principally by member 64 to ground through the frame. As described earlier, the lower shield member 40' functions in a similar manner to conduct radio energy in the region of the lower shield through the frame to ground. In this manner, the emission of stray energy exteriorly of the entire apparatus is essentially eliminated thereby eliminating the undesirable interference effects which such energy might otherwise have on electrical equipment in the area. The cover and lower shield member function additionally to provide a relatively constant capacitive load which prevents objects close to the apparatus from adversely affecting current distribution. In addition, as above noted, the lower shield is an integral part of the tank circuit and advantageously directs return current.

It will further be noted that cover 60 when closed effectively cuts off access to the electrodes so as to eliminate the possibility of inadvertent contact with the high-voltage electrodes by apparatus attendants or the like. The cover 60 is uniquely constructed to cooperate with the frame of the apparatus to provide openings at opposite sides of the apparatus through which the web material can pass. The depth of such openings can be simply regulated, and the vertical distance of the web from the electrodes can be similarly adjusted to vary as desired the heat created in the dielectric web material.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I therefore particularly point out and distinctly claim as my invention:

1. Apparatus for heating a traveling web of dielectric planar set of parallel electrode rods carried by said frame, a radio frequency generator, capacitor means electrically connected thereto, a second set of electrodes electrically connected to said capacitor means and alternately interposed between and parallel to said electrodes of said first setof electrodes to provide voltage gradients therebetween, first shield means below said electrodes and carried by said frame for conducting radio energy in the region of such first shield means to ground through said frame, and second shield means disposed above said elec trodes and operatively connected to said frame for conducting radio energy in the region of said second shield means to ground through said frame each of said first and second shield means comprising an outer conductive member fixed to said frame and an inner conductive member supported on said frame and spaced interiorly of said material comprising a grounded metal frame, a first outer member.

2. The combination of claim 1 wherein said second shield means comprises a cover, means for hinging said cover at one end thereof to said frame, said cover serving to enclose the top of said frame at both ends thereof, said cover being provided along the longitudinal sides thereof with vertically adjustable angle members adapted to be variably vertically spaced from angle members carried by said frame thereby to provide an opening at the sides of said apparatus through which such web can pass over said electrodes.

3. The combination of claim 2 further including means for vertically adjusting said angle members carried by said frame thereby to variably vertically space said web from said electrodes.

4. Apparatus for heating a traveling web of dielectric material comprising a grounded metal frame, a first planar set of parallel electrode rods carried by said frame, a radio frequency generator, capacitor means electrically connected thereto, a second set of electrodes electrically connected to said capacitor means and alternately interposed between and parallel to said electrodes of said first set of electrodes to provide voltage gradients therebetween, first shield means below said electrodes and carried by said frame for conducting radio energy in the region of such first shield means to ground through said frame, and second shield means disposed above said electrodes and operatively connected to said frame for conducting radio energy in the region of said second shield means to ground through said frame, said second shield means comprising a cover hinged at one end to said frame, said cover and said frame being provided with angle members at opposite sides thereof cooperable to form an opening through which said web can pass.

5. The combination of claim 4 wherein said angle members carried by said cover and said frame are vertically adjustable thereby to vary the width of the openings through which said web passes and the distance of said web from said electrodes.

6. The apparatus of claim 1 wherein said inner and outer members are coextensive and substantially enclose said first and second sets of electrodes.

7. The apparatus of claim 6 wherein said inner member of said first shield means is of shallow tub configuration, an inductance branch connected from between said capacitor and said radio frequency generator to said inner member, said capacitor and said inductance branch being disposed in the area formed by said inner member to establish a portion of the tuned circuit for said generator.

References Cited UNITED STATES PATENTS 3,357,108 12/1967 Bennett 219--10.61 X 3,364,294 1/1968 Garibian et a1. 2l910.6l X

JOSEPH V. TRUHE, Primary Examiner L. H. BENDER, Assistant Examiner 

